1. Field of the Invention
The present invention relates to a fuel injection type internal combustion engine provided with a pressure regulating device for maintaining a constant pressure difference between an inlet and outlet of a fuel injector.
2. Description of the Related Art
Known in the prior art is an electronic controlled fuel injection type internal combustion engine provided with a pressure control system for maintaining a constant pressure difference between the inlet and outlet of a fuel injector. In the electronic controlled fuel injection internal combustion engine, the amount of fuel to be injected is calculated in accordance with various engine operating conditions, and the injector is operated for a period allowing the calculated amount of fuel to be injected. The amount of fuel actually injected is, however, varied with the constant period of the operation of the fuel injector when the pressure difference between the inlet and outlet of the fuel injector is varied. Therefore a constant pressure difference must be maintained in order to obtain a precise control of the amount of the fuel to be injected.
A system has been proposed for maintaining a constant pressure difference wherein a pressure regulator is provided having a diaphragm which is operated by a pressure difference between a pressure of fuel from a fuel supply pump and a pressure of an engine intake line at a position where the fuel injector is mounted.
When the engine is started the opening of the throttle valve is small, so that the intake pressure in the sense of absolute pressure is small. As a result, the regulator system operates so that the pressure of the fuel supplied to the injector from the fuel pump is correspondingly decreased. The decreased pressure of the fuel causes the fuel to be vaporized in the fuel passageway when the engine is in a condition where the temperature of the fuel is high. Such a high temperature of the fuel will be generated in a situation such as that wherein the engine is stopped for a short while after high speed operation and then restarted. Due to the vaporization of fuel in the fuel passageway leading to the fuel injector, a so-called "vapor lock" is generated, causing difficulty in introducing the fuel into the fuel injector, making it difficult to easily start the engine.
To overcome this difficulty, a system is proposed wherein a detecting means is provided for detecting the condition of the high temperature of the engine to be started, and the detecting signal is supplied to the pressure regulator, thus opening the pressure regulator to the atmospheric pressure and cancelling the operation thereof. However, in this improved art, when the operation of the pressure regulator is cancelled, the pressure obtained in the regulator is at most atmospheric pressure, which is insufficient to allow the engine to be easily started. This also leads to an unstable idling operation.